In telecommunications, the amount of information that can be sent over a single optical fiber can be increased by sending information using multiple optical signals, each with a different wavelength. A WDM can be used at a transmitting end of the optical fiber to combine light from a group of optical fibers into the single optical fiber. On the receiving end of the optical fiber, another WDM can be used to demultiplex the multiple optical signals into another group of optical fibers.